1. Field of the Invention
The present invention relates to a magnetic head used in a hard disk device (hereinafter referred to as HDD) and a method of manufacturing the same. More specifically, the present invention relates to a magnetic head applicable to a magnetic recording medium having a high recording density, which has a diamond like carbon film or an amorphous like hydrogenated carbon film (hereinafter referred to as a DLC film) as a protective film, and a method of manufacturing the magnetic head for forming the DLC film.
2. Related Background Art
An HDD is one of external storage devices used in a relatively small computer system. As to the HDD, raising of recording density is being progressed in response to the reduction in size and the request for enlarging the storage capacity. As one of structural components of the HDD, there is given a magnetic head for actually performing write and read of information to a magnetic recording medium. Examples of the magnetic head include a so-called thin film head, a so-called AMR head or GMR head using a magneto-resistance effect, and a TMR head using a tunnel phenomenon. Raising of recording density is aimed at by selecting any of various magnetic heads described above.
A core portion in the magnetic head described above is constituted by an element portion for actually writing information or reading information from to a magnetic recording medium and a portion called slider (substrate portion) formed with the element portion on its end portion. Such a structure is adopted in which a predetermined surface of the slider and the element portion (end surface) are integrally floated and opposed with respect to the magnetic recording medium with a predetermined distance in the case where write of information or the like is conducted.
In the element portion, various metals such as a soft magnetism film constituting an element are exposed, and there is a fear that rust and the like develop in these metals, which leads to deterioration of the magnetic property and the like. Therefore, a protective film onto the surface of the element portion is formed, and various films having corrosion-resistance property are proposed for the protective film. Further, since the slider is floated from the recording medium by a wind pressure that is generated due to rotation of the magnetic recording medium, or the like to thereby maintain the above-described predetermined distance, low frictional performance is also required for the slider predetermined surface in order that the slider slides with ease and with low load in the initial stage of rotation.
In order to response to the above requests, the following is conducted in which the protective film is formed of a material having both the above-described corrosion-resistance property and low frictional performance on the surface of the substrate opposite to the magnetic recording medium and on an opposing part of the element portion opposite to the magnetic recording medium (hereinafter both are referred to as a film forming surface). DLC (diamond like carbon) is used as the material for the protective film in recent years.
As an example in which a DLC film is formed on the above-described film forming surface, there is given the magnetic head disclosed in Japanese Patent Application Laid-open No 9-63027. In that document, there is described that the DLC film is an amorphous film obtained by using plasma discharge, and so-called CSS (contact start stop) property in an HDD device is greatly improved by the formation of the DLC film. Further, there is described that, in order to obtain satisfactory wear or abrasion resistance property or satisfactory resistance in a CSS test, the DLC film needs to have a thickness of 20 Å or more and that, in order to improve adhesiveness between the DLC film and the film forming surface, it is effective that a silicon layer or a silicon carbide layer is formed as a base film.
A so-called flotation distance between the above-described film forming surface and the magnetic recording medium is desired to be smaller along with raising of recording density in recent years. From this point of view, in the protective film, it is necessary that the thickness is made thinner and sufficient corrosion-resistance property and low friction performance are maintained. According to Japanese Patent Application Laid-open No. 9-63027 described above, in order to obtain sufficient resistance (low frictional property) with the use of the DLC film, it is sufficient that the thickness is set to 20 Å or more, but in order to make the floatation distance small as well as maintain both the corrosion-resistance property and low frictional property, namely, in order to thin the thickness of the protective film, a method of forming a protective film or DLC film needs to be further developed.
Further, on the film forming surface, the substrate portion made of ceramic which is an insulator, and an insulating layer, a conductive layer, and a magnetic layer which exist in the element portion are exposed. Therefore, in case of using a film deposition method wherein species used for film deposition is generated by an electric discharge, for example, there is a fear that the potential difference develops in the film forming surface, and the film forming speed in the initial stage of the film deposition largely differs depending on a material of the film forming surface. In this case, it is considered that large variation in film thickness is caused, which means that there is caused the state in which, for example, the thickness of the DLC film locally becomes thin, or the film is not formed locally, and the local portion becomes a pin hole or the like, which leads to deterioration of corrosion-resistance property.
Further, in a general process of manufacturing a magnetic head, polishing processing is conducted to the film forming surface before undergoing the formation of the protective film, and few irregularities are formed on the surface. The film deposition speed generally differs between on a concave portion and a convex portion although this depends on where the irregularities exist among the insulating layer, the conductive layer, and the magnetic layer. Therefore, in the case where the film deposition speed is slow particularly in the concave portion, there is a fear that the portion remains as the pin hole, as a result of which the corrosion-resistance property is greatly deteriorated.
In terms of the corrosion-resistance property, there has been adopted the measure in the prior art in which, for example, the thickness of the DLC film is made thick, thereby obtaining the state in which no pin hole outwardly exists on the surface of the DLC film in order to make the influence of the pin hole or the like small as much as possible. However, in actuality, it has been difficult that the corrosion-resistance property is remarkably improved by means of the above measure, and also it has been difficult that the above-described demand for thinning the protective film is satisfied since the thickness of the DLC film has to be made larger than the thickness required.